Malignant cancers are the second leading cause of death in the USA with colorectal cancer being the second most fatal cancer. The elderly population is particularly at risk for colorectal cancer as its incidence increases with age. Circulating platelets are known to change with age which may affect a variety of degenerative diseases including cancers. Platelets are implicated in the promotion of carcinogenesis and its metastatic spread, and their circulating numbers are reported to be elevated in a number of solid tumors including colorectal cancer. Platelet aggregation with circulating cancer cells appears to protect the cancer cells and promote their metastasis. Recent studies of large populations of patients on low dose antiplatelet therapy (low dose aspirin) for cardiovascular risk reduction, have reported that aspirin confers significant protection against cancer formation, metastases and death. Thus, it is possible that the known chemopreventive activity of aspirin may be related to its antiplatelet action. Our hypothesis is that modulation of platelet activity i important for prevention of colorectal cancer and suppression of metastatic growth. One limitation to the widespread use of aspirin for chemoprevention is its side effect to induce acute gastrointestinal (GI) bleeding that may become life threatening if untreated. This is particularly problem for the elderly, as advanced age is a risk factor for NSAID-induced GI ulceration/bleeding. A recently FDA-approved aspirin product that is GI- safer (Aspirin-PC/PL2200) developed by the PI's laboratory may offer a means to provide significant chemoprevention with reduced GI side effects. We propose to investigate: 1) the in vitro cross-talk between platelets from young and elderly subjects and cancer cells, and their responsiveness to antiplatelet drugs, including various aspirin formulations, notably Aspirin-PC, and other agents; and 2) an in vivo colon cancer [models of both pre-cancer initiation] and metastatic growth in young and old animals for sensitivity to antiplatelet drugs. These studies will contribute to knowledge about the role of platelets in chemoprevention of colorectal cancer in the elderly, and may offer a timely and safe approach to reduce the metastatic spread of cancer in the elderly.